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Thursday is the anniversary of a fire in 1967 that killed three astronauts during a test aboard their Apollo spacecraft, and Saturday is the anniversary of the 1986 Challenger explosion that killed seven astronauts. The anniversary of the space shuttle Columbia disaster is Feb. 1.

NASA head Charles Bolden was at Arlington on Thursday to help lay wreaths in memory of the Challenger and Columbia astronauts as well as two Apollo 1 astronauts buried at the cemetery.